This project will utilize a resource of previously collected data to analyze familial clustering of cancer. The Utah Population Database combines the genealogical records of a stable population linked to a registry of all cancers occurring within the population since 1966. This Database permits the only known population-based analyses of familial clustering for all cancer sites. The resource served as a focus for research of approximately 20,000 Utah SEER records through 1980; approximately 10,000 additional records from 1981 through 1986 have now been linked and the database is being continuously updated. The complete data set now available will be analyzed for clustering of cancer among relatives using the genealogical index technique. In addition, the traditional epidemiologic analysis of relative risks for a cancer site given family history will be performed. The often cited hypotheses of coaggregation of different cancer sites within familial clusters will be tested. The set of all paired spouses who both have cancer of any site will be used to investigate the hypothesis of clustering of cancer due to familial, but non-inherited factors. Finally, specific subsites of cancer, for example by age, sex, or histology, will be analyzed for excess clustering. This project proposes many new analyses of interest on this unique data set, and the larger sample sizes which are now available permit reanalysis of more cancer sites and site subdivisions than have been previously analyzed with the genealogical index technique.